An assembly line is a manufacturing process in which parts are added to a product in a sequential manner to create a finished product much faster than is possible using handcrafting-type methods. The automotive industry is one example of an industry that utilizes assembly line manufacturing processes. Briefly, different manufacturing steps are performed repeatedly at various stations, which typically are arranged along main assembly lines and sub-assembly lines. By way of a specific and non-limiting example, truck frame front modules and rear modules are assembled at respective stations of sub-assembly lines, and are assembled together subsequently at a marriage station of the main assembly line. Efficiency is achieved in an assembly line manufacturing process due to the division of labor and specialization that results from individuals performing the same task over and over, and due to the fact that many different steps of the assembly process can be performed simultaneously at different stations along the assembly line.
Today, industrial robots perform many of the tasks at the different stations of an assembly line manufacturing process, such as for instance welding, riveting, bolting, painting etc. In a typical automobile assembly line, each station is based on a dedicated tool including a base that is mounted to the floor. A plurality of tooling elements is mounted to the base, providing a predetermined arrangement of tooling elements for performing predetermined assembly steps of the assembly of a predetermined product. These bases have standard heights, widths, and mounting patterns and can be removed and replaced by other bases, having different tooling elements mounted thereto, when it is necessary to retool the assembly line in order to make a different product. Continuing with the truck frame assembly example, the tooling elements that are mounted to the base module may include fixtures for holding the individual frame components in a secure fashion while robots fasten the frame components together, such as by welding.
Of course, an assembly line is most efficient when it is used to produce only one type of product. In that case, every product that comes off the assembly line is identical, and there is no need to change the arrangement of the tooling elements that are employed in the assembly line. Accordingly, the amount of downtime of the assembly line is minimized.
Unfortunately, vehicle purchasers have varying requirements and preferences, and therefore it is not desirable for a manufacturer to offer just one type of vehicle. For instance, the Ford Motor Company offers a number of different truck families, including the F-150, F-250, F-350, F-450, and F-550. Within each family, a number of different length variants are also available, such as for instance the F-150 regular cab with a 6.5′ box, the F-150 regular cab with an 8′ box, the F-150 super cab with a 6.5′ box, the F-150 super cab with an 8′ box and the F-150 super crew. It would be impractical to build and operate a different assembly line facility for manufacturing each one of the above-mentioned truck variants. Rather, in view of the high capital costs that are associated with modern automotive assembly line facilities, it is necessary to use the same assembly line for manufacturing a plurality of length variations within a family of vehicles, or even for manufacturing entirely different families of vehicles.
Clearly, a problem may arise when the decision is made to stop production of one product, such as for instance the F-150 regular cab with a 6.5′ box, and begin production of a different product, such as for instance the F-150 regular cab with an 8′ box. In this specific and non-limiting example, the different length of the longitudinal frame rails and/or the different spacing between cross members in the two types of truck frames necessitates a different mounting arrangement of the tooling elements on the base modules. Further, different types of truck frames may require different processes, for instance joining by welding instead of, or in addition to, riveting.
Since the stations of a typical assembly line are based on dedicated tools, in order to assemble a different product it is necessary to remove and replace the bases and associated tooling elements of the assembly line with different bases having different associated tooling elements. Unfortunately, the process of switching the dedicated tools is currently done manually and results in substantial downtime, ranging from between typically half an hour to half a day, depending on the nature of the differences between the current product and the next product.
Prior attempts have been made to mitigate some of the problems that are encountered when assembly line production is switched from one product to another. For instance, in order to accommodate different vehicle frame lengths it is known to put part of a dedicated tool on pneumatically driven sliders, which are mounted onto a base. According to this approach, a fixed tool is provided with a limited amount of variability for accommodating different rear frame modules. When production is switched from one product to another, the sliders are driven to a predetermined location that depends upon the length of the new product. Unfortunately, idle stations are required when this solution is implemented since the sliders can be used to adapt the tool to accommodate only a limited amount of length variation.
It would be desirable to provide a method and a system that overcome at least some of the above-mentioned limitations of the prior art.